Magnetic speedometer.



l. K. STEWART, DEC'D.

)- B- STEWART, EXECUTRIX.

menanc spzwommn.

APPLICATION FILED SEPT-12,19l6. 1,238,455, Patented Aug. 28, 1917.

UNITED STATES PATENT OFFICE.

[OHN K. STEWART, DECEASED,.BY JULIA. B, STEWART, EXECU'IBIX, OFNORTHPOBT,

new roan; ETEB coarona'rron,

SAID JOHN K.

STEWART ASSIGNOR OF CHICAGO, ILLINOIS, A CORPORATION OF VIRGINIA.

TO STEWART-WARNER SPEEDOM- MAGNETIC SPEEDOMETEB.

Specification of Letters Patent.

Patented Aug. 28, 1917.

Orlglnal application filed January 27, 1918, Serial No. 744,343. Dividedand this application filed September 12, 1916. Serial No. 119,643.

T all whom it may concern:

Be it known that I, JULIA B. STEWART, a citizen of the United States,residing at Northport, in the county of Suffolk and State of New York,am the executrix of the last will and testament of JOHN R. STEWART,deceased, who had invented new and useful Improvements in MagneticSpeedometers, of which the following is a specification, reference beinghad to the accompanying drawings, forming a part thereof.

This application is a division of the a plication of John K. Stewart,Serial 0. 744,313, filed January 27, 1913, now Patent No. 1,200,899,dated October .10, 1916.

The invention to which this application relates is an improvement inmagnetic speedometers, particularly with respect to means for dampingthe vibrating or oscillating element to make it what is commonly calleddead-beat. It consists in the elements and features of constructionshown and described, as indicated in the claims.

* In the drawings:

Figure 1 is a front elevation of an instrument embodying this invention,the face plate being broken away to disclose the structnre and themagnets and the drag element being shown in diametric section at theline, 1-1, on Fig. 2.

Fig. 2 is a detail view of a modification, the parts being seen lookingin the same direction as in Fig. 1, the drag element being partly brokenaway to disclose the magnet underneath.

As shown in the drawings, this invention is embodied in a magneticspeedometer of familiar type which comprises a magent, A, rotatablymounted upon a shaft, B, for influencing a drag element, carries thespeed-indicating scale, C, readable at the window, D, in the face plate,D. To overcome the liability of the drag element to be over-actuated bysudden changes of speed of rotation of the magnet, and in consequence tooscillate back and forth and fail to give a steady indication, that is,to fail to be what is commonly called dead beat, there is mounted uponthe frame bar, D, a light spring arm, which carries at its free end abutton, F, of magnetic material positioned to overhang the path ,ofrotation of the notch or gap, 1, in the ring C, which latter magnet, A,or, in effect, over the path of rotation of the poles of the magnet, sothat every time said notch or the magnet poles pass under the button, Fin the rotation of the magnet, the button is drawn downwardly by themagnetic force acting against the yielding resistance of the spring arm,F, and bring the button, or its spring finger hereinafter mentioned, incontact with the upper surface of the drag member, C, for the in stantthat the poles are passing the button, the reaction of the spring armretracting the button as soon as the poles have passed. The momentarycontact with the button, or its spring finger hereinafter mentioned,with the drag disk serves to check its oscillation without preventing itfrom eventually obtaining the movement which it should derive from thedrag action of the magnet, but preventing it from having any longuninter rupted swing which would cause it by momentum to swing fartherthan the natural drag action of the magnet would cause it to swing, andit is thus rendered dead heat, and steady in its indication of the speedwhich it is the purpose of the instrument to indicate.

Preferably, in order that the contact produced by the attraction of themagnet for the armature button may be suitably soft, and thereby notliable by its frequent repetition to distort the disk or mar itssurface, there is shown connected with the button a light spring arm, Fwhose end portion makes the contact with the disk when the armaturebutton is drawn down by the magnet pole.

I claim 1. In a magnetic speedometer, comprising a magnet mounted forrotation of its poles about an axis, and a drag disk mounted proximateto the path of rotation of sai poles, a damping device for said dragdisk comprising an armature positioned proximate to the path of rotationof the magnet poles and mounted for movement toward and from saidmagnet, means adapted for yieldingly holding said armature away from themagnet and a brake device connected with the armature for movementtoward and against the drag disk.

2. In a magnetic speedometer comprising a magnet mounted for rotation ofits poles about an axis, and a drag disk mounted proximate to the pathof rotation of said poles; an armature button also positioned proximateto the path of rotation of the poles and mounted for movement toward andfrom the magnet; a spring connected with said armature for holding itaway from the magnet and a flexible brake arm extending from thearmature button for con tact with the drag disk when the button iattracted by the magnet noles.

In testimony whereof, I have hereunto se my hand at Northport, L. I.,this 8th day 01 September, 1916.

JULIA B. STEWART,

Ewecutm'm of John 11.. Stewart, deceased.

